Long-term changes of standing balance after lateral ankle sprain using Footscan system: A case report

Rationale: A lateral ankle sprain (LAS) is a common sports related injury. Ankle instability and balance impairment after injury are common. This case report describes the longitudinal changes in static balance after LAS. Patient concerns: A 36-year-old man visited our hospital with LAS of the right ankle that occurred during an exercise session. The patient complained of severe pain and swelling of the ankle. The patient was unable to walk a short distance. Diagnoses: Ultrasound examination showed swelling of the surrounding soft tissues and a partial tear of the right anterior talofibular ligament. In the Doppler scan, vascularity increased around anterior talofibular ligament. No fractures were observed on computed tomography. Interventions: The patient received analgesics for pain control. The rest, ice, compression, elevation protocol was used. The injured area was protected with a controlled ankle movement walking boot for 2 weeks. Standing balance was measured at 3, 4, 8, 12, and 24 weeks after injury using Footscan. Outcome: He was able to walk approximately 2 weeks after the injury with reduced pain over time. It was observed that the standing balance improved over time. Lesson: In this case, it was objectively confirmed that standing balance was restored naturally after LAS.


Introduction
Acute ankle sprain is a common musculoskeletal injury among athletes.It can be divided into lateral, medial and high/syndesmotic ankle sprains according to the location of the lesion.Lateral ankle sprain (LAS), accounting for about 73% of these, are one of the most common musculoskeletal injuries associated with exercise. [1]One meta-analysis study reported that athletes had a prevalence of 0.93 LAS per 1000 matches or exercises. [2]LAS is caused by hypersupination of the ankle.The most commonly involved ligaments are the anterior talofibular ligament and calcaneofibular ligament. [3]The diagnosis of LAS is usually diagnosed based on the patient's medical history.However, in severe cases, complications such as fracture or rupture of the ligament, may occur.Therefore, additional radiography, ultrasonography, or magnetic resonance imaging may be performed according to the Ottawa ankle rules. [4]AS have been shown to recur in 11.9% of cases, [5] and may lead to pain that persists after the acute phase and decreased physical ability.[8] It can also induce osteoarthritis in the long run. [9,10]hronic ankle instability due to LAS causes laxity and mechanical instability, which can make standing balance unstable. [11]Few quantitative studies have been conducted regarding this matter.In this study, quantitative measurement of long-term changes in static standing balance after LAS was performed using a plantar force measuring plate called the Footscan system.

Case presentation
An amateur tennis player, height 177 cm, weight 75 kg, 36 years old male, stepped on a tennis ball with his right foot and sprained his ankle.His right ankle had abrupt and excessive plantarflexion and inversion.Swelling, pain and tenderness were observed on the lateral side of the ankle.After the injury, the patient was unable to walk for more than 4 steps.No fracture was identified on computed tomography.Ultrasonography revealed a partial tear in the right anterior talofibular ligament and increased vascularity of the surrounding soft tissues (Fig. 1).
Based on the symptoms and ultrasound findings, the patent was diagnosed with grade II ankle sprain. [12]He received analgesics for pain control and the rest, ice, compression, elevation protocol. [13]A controlled ankle movement walking boot was applied for 2 weeks (Fig. 2).After 2 weeks, his pain and swelling reduced and he could walk independently in an antalgic gait pattern without a controlled ankle movement walking brace.The patient did not participate in any rehabilitation exercise program.Ankle sprain did not recur during the follow-up period.
Periodic follow-up examinations were performed to measure the standing balance using Footscan.It is a tool that can quantitatively measure the pressure delivered to the foot through a 1m long plantar force measuring plate that consists of 8192 pressure sensors (Fig. 3).Footscan examinations were conducted 3, 4, 8, 12, and 24th weeks after injury.In each session, the examinations were performed 3 times and the result were averaged.To confirm the changes in standing balance, we measured the travel distance for the center of pressure (COP) and the weight distribution of 4 quadrant areas: right, left, anterior, and posterior (Fig. 4).
The travel distance of the COP was longest in the 3rd week and decreased thereafter (Fig. 5).The weight distribution in the 4 quadrants remained similar without significant variability (Fig. 6).

Discussion
This case study describes quantitative changes in static standing balance in patients after LAS.Balance parameters were obtained using Footscan.The main indicator of static balance was the travel distance of the COP.In addition, the weight distributions of the 4 quadrants were obtained.In our study, there was improvement in static balance over time.The weight distribution between injured and uninjured feet did not differ significantly during the entire observation period.
Patients after LAS often show an antalgic gait pattern and develop poor balance towards the involved limb. [14]The causes of such functional instability include balance deficit, joint position sense deficit, and delayed peroneal muscle reaction time. [11]Previous studies have reported that the improvement of balance was obtained after improving proprioception of the affected ankle in patients with LAS.[17] In addition, after short-term pain and impaired balance, subsequent chronic ankle instability or osteoarthritis should be considered.Therefore, examination and follow-up  of balance impairments, caused neuromuscular deficits are essential.
Among the previous studies, there have been many studies on how balance after LAS changes.One study used balance parameters such as postural sway (deviation from the COP) [18] or the Rhomberg test. [19]Most of these studies evaluated immediately after injury, making it difficult to determine changes over time.Furthermore, there were some limitations that these kind of parameters were insufficient to be objective or quantitative.Few studies have been conducted over the years.In this respect, we used Footscan to confirm changes in static balance for half a year to overcome these limitations.
This case report is meaningful in that it carried out a serial follow-up evaluation, up to approximately 6 months after the injury.The limitation of this study is that there was no pre-injury test, so we do not know the baseline condition.Future studies with multiple subjects are needed to confirm this relationship.From this study, we learned about the usefulness of Footscan as a means of monitoring balance changes after LAS.

Conclusion
A 36-year-old man visited our clinic with Grade II LAS.Over the following months, the patient showed reduced pain and could walk independently with improved static balance on the Footscan.In this study, we found that static balance, which reduced after LAS, was restored over time.

Figure 4 .
Figure 4.The weight distribution by four quadrants.

Figure 5 .
Figure 5.Time dependent change of travel distance on Footscan.

Figure 6 .
Figure 6.Time dependent change of weight distribution on Footscan.